The present invention relates to a liquid crystal display (LCD), and more particularly to such a display wherein each of the alignment layers is made of a different material.
A LCD comprises a pair of substrates with one or more electrodes on each substrate. An alignment layer overlies each electrode, and a polarizing layer is disposed on the outside of each of the substrates. Further, for a color LCD, a color filter overlies one substrate enclosed in an encapsulating layer lying between the electrode and the substrate. A liquid crystal material (LCM) is disposed between the alignment layers. The alignment layers align the LCM to a selected "tilt angle", which is the angle between the longitudinal axis of a liquid crystal molecule and the plane of the alignment layer. The alignment layers cannot require a cure temperature that is so high that damage to the drive electronics and the color filter can result. While low curing temperature alignment materials exist, they also have a low tilt angle. A low value for the tilt angle can result in ambiguities in the way the LCM aligns with the layer and a long response time. By "ambiguities" is meant that different portions of the LCM within an LCD align with different optical rotations. Further, some alignment materials allow ionic migration from the substrate into the LCM.
It is therefore desirable to have an LCD whose alignment layers do not require a curing temperature that damages the electronics or color filters during fabrication, have a minimum of twist ambiguities, and minimize ionic migration.